本文描述了使用javascript读取用户通过Input控件选择的文件的内容的方法和注意事项。后面用英文写，但我的英文不太好，如有错误之处，希望大家帮我纠正，我的联系方式在后面。
When user select a file by <input type=file>, its content can be read by javascript like this:187Please respect copyright.ＰＥＮＡＮＡc1ZmkMJfJm
---read whole file content into array buffer---187Please respect copyright.ＰＥＮＡＮＡ79mUCbxWTi
let file=input.files[0]; const reader = new FileReader(); 187Please respect copyright.ＰＥＮＡＮＡI1zAo8rHoQ
reader.onload = () => 187Please respect copyright.ＰＥＮＡＮＡp3FQ8qZh70
{187Please respect copyright.ＰＥＮＡＮＡ2GL4pL76Bo
let content_whole = new Uint8Array(reader.result);187Please respect copyright.ＰＥＮＡＮＡo0LX9o8OXt
}187Please respect copyright.ＰＥＮＡＮＡceHxUc3ksa
reader.readAsArrayBuffer(file);187Please respect copyright.ＰＥＮＡＮＡ8gzmIJPg4I
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If the file size is too large, the browser may crash as the whole file content are loaded into memory by array buffer. In order to avoid it, we can just read a part of the file like this:187Please respect copyright.ＰＥＮＡＮＡOYthdp5Ova
---read part of file content into array buffer---187Please respect copyright.ＰＥＮＡＮＡL1wnTWmPwZ
let file=input.files[0], block_size=1000000, start=0, end=block_size; const reader = new FileReader(); 187Please respect copyright.ＰＥＮＡＮＡOHpB5F7Bvg
reader.onload = () => 187Please respect copyright.ＰＥＮＡＮＡ0ZpsPOAq7W
{187Please respect copyright.ＰＥＮＡＮＡJLYFSGu5V3
let content_part = new Uint8Array(reader.result);187Please respect copyright.ＰＥＮＡＮＡ16WCnOEoDY
}187Please respect copyright.ＰＥＮＡＮＡhVmiN6qoNp
reader.readAsArrayBuffer(file.slice(start,end));187Please respect copyright.ＰＥＮＡＮＡElhvWLRNVd
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187Please respect copyright.ＰＥＮＡＮＡhSs1Q685sb
Section X. Thanks187Please respect copyright.ＰＥＮＡＮＡwlx9PThzcC
https://segmentfault.com/a/1190000022113605
Section Y. Contacts Me
If you found any errors or have any suggestions for this article, please let me know, my wechat: si_jinmin, my email: [email protected]187Please respect copyright.ＰＥＮＡＮＡ2U9KrtxnMU
如果您发现本文有任何错误，或者对本文有好的建议，欢迎与我联系探讨，我的微信: si_jinmin, 我的email: [email protected]
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